Influence of psychotropic drugs on traffic safety is a great problem at present. Forensic expertise of their influence on the ability to drive a car is much more complicated than in alcohol. Elimination of these compounds does not enable us to calculate the drug blood level at the time of accident, their influence on psychic functions is much more variable than in alcohol and we can observe toxic psychoses more often than after alcohol, too. The authors conclude that a zero blood level of „illicit drugs“ is an essential condition of the ability to drive a car.

        Key words: non-alcoholic psychotropic substance, illicit drug, traffic safety, driving, psychiatric forensic expertise.